Vascular Retinopathies

An interruption in blood supply to the eye can produce a vascular retinopathy, which is a noninflammatory retinal disorder. Common vascular retinopathies include central retinal artery occlusion, central retinal vein occlusion, diabetic retinopathy, and hypertensive retinopathy.

Central retinal artery occlusion occurs unilaterally and affects elderly patients. The prognosis is poor­in 5% to 20% of patients, secondary glaucoma develops rapidly 3 to 4 months after occlusion.

Central retinal vein occlusion, most prevalent in elderly patients, causes vision loss more slowly than central retinal artery occlusion.

Diabetic retinopathy is the leading cause of blindness among people ages 20 to 44. About 40% of patients who have had type I diabetes and about 25% of those who have had type II diabetes for 10 years develop retinopathy. After 15 years, the disorder develops in about 95% of people with type I diabetes and in about 50% of those with type II diabetes. At additional risk are pregnant patients, blacks (who have a 20% greater risk than whites), and women (who have a 23% greater risk than men).

Causes

When a retinal vessel becomes obstructed, the diminished blood flow causes visual deficits. Central retinal artery occlusion may be idiopathic or may result from embolism, atherosclerosis, infection, or conditions that retard blood flow, such as temporal arteritis, carotid occlusion, and heart failure.

Central retinal vein occlusion may result from external compression of the retinal vein, trauma, diabetes, thrombosis, granulomatous diseases, generalized and localized infections, glaucoma, and atherosclerosis.

Diabetic retinopathy results from diabetes, which causes microcirculatory changes. These changes occur more rapidly when diabetes is poorly controlled.

Hypertensive retinopathy results from prolonged hypertension, which produces retinal vasospasm and consequent damage to and narrowing of the arteriolar lumen.

Diagnostic tests 

Appropriate tests depend on the type of vascular retinopathy. Evaluation needs to include visual acuity findings and ophthalmoscopic examination.

Treatment

No particular treatment is known to control central retinal artery occlusion. However, an attempt is made to release the occlusive plaque or emboli into the peripheral retinal circulation. To reduce intraocular pressure, therapy includes acetazolamide 500 mg I.V., eyeball massage with a Goldman-type goniolens and, possibly, anterior chamber paracentesis. Therapy also includes inhalation of carbogen (95% oxygen and 5% carbon dioxide) to improve retinal oxygenation. Because inhalation therapy may be given hourly for up to 48 hours, the patient requires hospitalization for close monitoring of vital signs.

Therapy for central retinal vein occlusion may include aspirin, which acts as a mild anticoagulant. Laser photocoagulation may reduce the risk of neovascular glaucoma for some patients whose eyes have wide­spread capillary nonperfusion.

Treatment for patients with early-stage, nonpro-liferative diabetic retinopathy is prophylactic. Careful control of the patient's blood glucose levels during the first 5 years of diabetes may decrease the severity of retinopathy or delay its onset. For the patient with microaneurysms, therapy should include frequent eye examinations (three or four times yearly) to monitor the condition. For a child with diabetes, therapy should include an annual eye examination by an ophthalmologist.

The treatment choice for patients with proliferative diabetic retinopathy is laser photocoagulation. This process involves cauterizing the weak, leaking blood vessels. Laser treatment may be focal (aimed directly at new blood vessels) or panretinal (placing as many as 2,000 burns throughout the peripheral retina). Despite such treatment, neovascularization doesn't always regress, and vitreous hemorrhage, with or without retinal detachment, may follow. If the leaked blood isn't absorbed in 3 to 6 months, vitrectomy may be performed to restore partial vision.

Treatment for patients with hypertensive retinopathy includes controlling blood pressure with appropriate drugs, diet, and exercise. Adherence to this regimen typically resolves ocular signs and symptoms.

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